feat: add Copilot enterprise usage reporting scripts

[joshjohanning]

Summary

• add a monthly enterprise usage report with weekly CSV and standalone HTML output
• add a per-user and model AI credit usage export
• use the active gh auth credential and provide access guidance for 404 responses
• document both scripts and their API limitations

Validation

• bash -n for both shell scripts
• repository README lint for gh-cli and scripts

[Copilot]

Pull request overview

This PR adds two new automation scripts to generate GitHub Copilot enterprise usage reporting outputs, along with README documentation updates so the scripts are discoverable and their limitations/permissions are clear.

Changes:

• Added a scripts/ utility to generate a monthly enterprise usage report with weekly CSV and a standalone HTML report
• Added a gh-cli/ utility to export monthly Copilot AI credit usage broken down by user and model
• Updated scripts/README.md and gh-cli/README.md to document the new scripts and key API constraints

Show a summary per file

File	Description
scripts/README.md	Adds the new usage-report script entry to the scripts index
scripts/copilot-enterprise-usage-report/README.md	Documents outputs, prerequisites, permissions, and usage for the new report script
scripts/copilot-enterprise-usage-report/copilot-enterprise-usage-report.sh	New script that downloads daily enterprise metrics and produces weekly CSV + self-contained HTML
gh-cli/README.md	Documents the new AI credit usage export script and its rate-limit implications
gh-cli/get-copilot-ai-credit-usage-by-user-and-model.sh	New script that identifies users with AI credit usage via daily metrics then exports per-user per-model billing usage

Review details

Suppressed comments (1)

scripts/copilot-enterprise-usage-report/README.md:38

• The Usage section includes both a generic invocation and a separate example block. To match the repository README guidance (keep just one), consider combining them into a single snippet and removing the separate Example block.

Example:

```shell
./copilot-enterprise-usage-report.sh avocado-corp 2026 7

</details>


- **Files reviewed:** 5/5 changed files
- **Comments generated:** 5
- **Review effort level:** Lite